#include<iostream>
#include<vector>
using namespace std;

int main(){
    vector<int> vi{1,2,3,4,5};
    for(auto num: vi){
        cout<<num<<" ";
    }
    cout<<endl;

    /* 引用， 改变原vector */
    for(auto& num: vi){
        cout<<num<<" ";
    }
    cout<<endl;
    return 0;
}